Mixed Iigand complexes of Ni(II) with alkylxanthates and
ditertiary phosphanes of the composition Ni(ROCSSb(diphoshhave
been prepared, where R = methyl, ethyl, propyl, butyl, and cyclohexyl
and diphos = bis(diphenylphosphino)ethane (dpe) and bis-
(diphenylphosphino)butane (dpb). The newly prepared compounds
were characterized on the basis of chemical analyses, infrared and
electronic spectra, lH-NMR, molar conductance, and thermal analysis.
A square planar structure was proposed for the complexes

Aref A. M. Aly

Asma I. El-Said

Mahmoud S. El-Meligy

Mostafa M. Kamal

English

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CROATICA CHEMICA ACTACCA-1788CCACAA 61 (I) 155-161 (1988)YU ISSN 0011-1643UDC 546.74NoteNew Mixed Ligand Complexes of Ditertiary Phosphanes withNi(II) AlkylxanthatesAref A. M. Aly, Mostafa M. Kamal, Mahmoud S. EI-Jl:Ieligy,and Asma t. El-SaidChemistry Department, Faculty of Science, Assiut University, Assiut, EgyptReceived May 14, 1987Mixed Iigand complexes of Ni(II) with alky;lxanthates andditertiary phosphanes of the composition Ni(ROCSSb(diphoshhavebeen prepared, where R = methyl, ethyl, propyl, butyl, and cyclo-hexyl and diphos = bis(diphenylphosphino)ethane (dpe) and bis-(diphenylphosphino)butane (dpb). The newly prepared compoundswere characterized on the basis of chemical analyses, infrared andelectronic spectra, lH-NMR, molar conductance, and therrnal ana-lysis. A square planar structure was proposed for the complexes.INTRODUCTIONCurrent inter est in simple and mixed metal complexes of xanthates stemsfrom their importance as insecticides and fungicides,' their use in vulcanizationof rubber," as antioxidants," and as lubricants-, For some years xanthato metalcomplexes have been extensively studied." Xanthatonickel(II) complexes str on-gly interact· with Lewis bases containing nitrogen, oxygen and phosphorousdoner atoms.6,7,8Furthermore, phosphorous ligands are known to be involved in variouscatalytic reactions of transition metals and the steric and electronic charactersof these ligands are extremely important in such reactions.? To our knowledgeno work has yet been done on the interaction of diphosphanes with alkyl-xanthatonickel(II}. Therefore, we wish to report in this artiele the preparationand characterization of some new mixed ligand complexes of alkylxanthato-nickel(II} and two ditertiary phosphanes vz. bis(diphenylphosphino}ethane (dpe)and bis(diphenylphosphino}butane (dpb).R = methyl, Mexan;= propyl, Prxan;= cyclohexyl, CyxanPh2P-(CH2)2-PPh2dperR = ethyl, EtxanR = butyl, BuxanPh2P-(CH2)4- PPh2dpb156 A. A. M. ALY ET AL.RESULTS AND DISCUSSIONThe reaction of alkylxanthatonickel(II) with ditertiary phosphanes pro-ceeds readily to give the corresponding mixed ligand complexes in high yield.Ni(ROCSS}z + 2Ph2P(CH2)nPPh2 -+ Ni(ROCSS)2(Ph2P(CH2)nPPh2)2 (1)(R = Me, Et, Pr, Bu and Cy; n = 2 or 4).It is of interest to note that, although phosphanes and alkylxanthato-nickel(II) were mixed in the molar ratio 1 : 1, only a 2 : 1 stoichiometry wasobtained for the corresponding mixed ligand complexes.The complexes are stable in air; they are soluble in chloroform, dirne-thylformamide, dimethylsulphoxide, insoluble in benzene, alcohol or acetone.The complexes are reported in Table I together with their analytical data,melting point and colour.IR DataAssignments are made on the basis of previously published IR data onmetal complexes of xanthates and their mixed ligand complexes.8,10,l1,12 Aband appears at 1180 cm? for all the complexes, which we assign to theC-O-C asymmetric stretching mode. This band comes at a considerablylower frequency than usual for alkylxanthatonickel(II) complexes.w-P Thisobservation suggests a change of coordination mode of the alkylxanthatesfrom bidentate to monodentate ligands upon interaction with phosphanes,which is in accord with previous reports." Symmetric vibration of C-O-Coccurs at about 1090 cm-I. Further, the band observed in the region 1020-1030cm'? appears to be associated with the C=S frequency; this range is alsoexhibited by mixed ligand complexes containing monodentate xanthates." Weassign the band at 475 cm" as a bending mode of the ligands.!' It could beinferred that the extra bands in the 700-780 cm-i, absent in the spectraof xanthatonickel(II), are due to -CH2(rocking) and PPhz-frequencies of thecoordinated phosphanes.PElectronic Spectral DataPertinent absorption bands of chloroform solutions of the complexestogether with their tentative assignments are shown in Table I. Two prominentbands are seen in the regions 18,100-20,010 and 21,210-23,240 cm'" assignableto the d-d transitions lAJg -+ lA2g and lAJg -+ lB1g, respectively. This maysuggest a square planar configuration of the central atom.l- The relativelyhigh intensity of the two bands may be attributed to the strong 11: interactionof nickel-phosphcrous and/or nickelsulphur bonds.š-v' The spectra of thepresently prepared complexes bear a remarkable resemblance to thosereported for analogous dithiolatonickeJ(II) mixed ligand complexes.P." forwhich a square plan ar stereochemistry was proposed. It seems reasonable toassign the bands in the range 25,000-27,710 cm'" to charge transfer transitionswhile those in the region 31,540-32,250 cm'" to a transition of the type 11: - 11:*.Addition of chloroform solutions of dpe and dpb in various molar ratios(vz. 1: 0.5, 1: 1, 1: 1.5, 1: 2, 1: 3, 1: 4) to chloroform solutions of the bis-Electronicspectra(cm'")AnalyticaldataM~CompoundColourm.p.Yield.Il~eSCo/oHO/oSo/o(Co)ttCT:n;-:n;*(calc.)(calc.)(calc.)~eco~~o s::: "o t<Ni(Mexanh(dpeh(62.87)(5.08)(11.98)lightred180801418,100t<J21;21025,63032,200~63.205.1411.00(decomp.)27.720t<J inNi(Etxanh(dpeh(63.45)(5.31)(11.68)orange190851218,51021,21026,33031,530o64.225.3812.00(decomp.)27,720"J ~Ni(Prxanh(dpeh(64.00)(5.54)(11.39)orange183801118,11021,25026,33032,24H64.945.74n.28(decomp.)27,710,!:jNi(Buxanh(dpeh(64.53)(5.76)(11.11)orange192751318,55021,26027,71031,540:<> t<64.325.8311.84(decomp.)~ ><Ni(Cyxanh(dpeh(65.72)(5.84)(10.63)yellow195651319,22021,54027,71032,220t< ~65.505.8010.72(decomp.);p ZNi(Mexanh(dpb)2(64.00)(5.54)(11.39)pale210701420,010-25,00029,820>-l ::r163.755.6510.68brown(decomp.)27,71032,220;p >-lNi(Etxanh(dpbh(64.52)(5.76)(11.11)grey2187312-23,21027,01031,750t<J64.215.5110.89(decomp.)32,220tnNi(Prxanh(dpbh(65.03)(5.96)(10.84)pale2206313-23,24027,01031,73065.226.0210.05yellow(decomp.)32,250Ni(Buxanh(dpbh(65.50)(6.16)(10.59)grey213601419,63023,24027,02031,74065.816.389.95(decomp.)32,220Ni(Cyxanh(dpbh(66.60)(6.22)(10.16)pale215621318,83021,27027,02032,25065.976.1010.51yellow(decomp.)I-'CJ1-J158 A. A. M. ALY ET AL.(alkylxanthato)nickel(II) (at constant concentration of 5 X 10-3 M) causes adecrease in the absorbances of the xanthatonickel(II) spectra. A small redshift in the bands of the xanthatonickel(II) complexes was noticed (about1,000 cm " for the system dpe/Ni(ROCSSh and no appreciable shift wasobserved for the system dpb/Ni(ROCSSh thus confirming the square planarstructure of the resulting complexes. An isosbestic point appears in case ofthe system dpb/Ni(ROCSSh suggesting the following equilibrium to occur:Ni(ROCSS)2+ 2Ph2P(CH2)nPPh2:.= Ni(ROCSSlz(Ph2P(CH2)nPPh2)2 (2)n = 2 or 4Typical spectra of Ni(Cyxan)z plus dpb at different mol ar ratios aredepicted in Figure 1. The plot of absorbance against molar ratio gives a breakat 2 : 1 molar ratio indicating the formation of 2 : 1 mixed ligand complexesin solution. This is in contrast to the spectrophotometric titration (at the samemol ar ratios) of dithiocarbamato - and dithiocarbazatonickelffI)!" with ditert-iary phosphanes, where only 1: 1 mixed ligand complexes were formed insolution (except for the system dpe/bis(phenyldithiocarbazato)nickel(II) whichforms both 1 : 1 and 1 : 2 mixed ligand complexes in solution); it was suggestedthat the 2 : 1 mixed ligand complexes undergo a rapid dissociation to the 1 : 1mixed ligand complexes.0·60·40.230.3 27.0 24.4 22.2 kKFigure 1. Absorption spectra of the system dpb/Ni(Cyxan)2 at different molar ratios(ratio in parentheses): 1 (O: 1); 2 (0.5: 1); 3 (1: 1); 4 (1.5: 1); 5 (2: 1); 6 (3: 1); 7 (4: n.COMPLEXES OF Ni (II) ALKYLXANTHA TES 159Conductivity DataConductivity measurements in DMSO indicate that the complexes areessentially non-electrolytes (Table I).lH-NMR DataThe lH-NMR spectra of the complexes in deuterated chloroform showthe protons of the phenyl group s of phosphanes (dpe and dpb) in the rangeo 7.4-7.9 ppm as two sets of multiplets which integrate in the ratio 2: 3;it suggests that ortho-proton signals appear down-field compared to meta- and para protons. In addition, in the region o 1.0-4.3 ppm, the spectrashow the characteristic resonances of the alkyl groups of xanthate ligands andthe -(CH2)n- of the phosphanes; the spectra are rather complicated in thisregion.Thermal DataThe TGA curves of the complexes in the temperature range 100~700 °cconsist of three stages of weight loss. The first weight loss occurs in the range180-210 DCwhich is consistent with the elimination of an aldehyde molecule(eq. 3). Elimination of aldehydes during the thermal decomposition of xan-thates is-R'CHONi(ROCSS)2(Ph2P(CH2)nPPh2}z , Ni(ROCSS) (HCSS) (PhzP(CHZ)nPPhZ)Z (3)n = 2 ar 4known in the Iiterature.P Beyond 210DC decomposition continues with theloss of ligands up to 400DC (second step). From this last temperature up to700DCthe third decomposition step is observed; the end product is identified(on the basis of IR spectra) as Ni2P207.A typical TGA thermogram of Ni(Me-xanh(dpe)z is shown in Figure 2.8; 1I!I!•:..61!2""~~~1~""~~2~""~~3~""~~4~"-"-+-~~"-+-B~"~I!-+-7-I!~I!~Temperature (OC)Figure 2. TGA thermogram of Ni(MexanJ2(dpeJ2,160 A. A. M. ALY ET AL.In view of the previous discussion it is to be concluded that the preparedcomplexes may have either of the following two structures:Php5.-( CHZ )~~~ -S-C~~R:"'-. /: .I Ni:/ <, :/(CHZ);;--'RO-C-S--------p p~S PhZ PhZ(I)Unfortunately, on the basis of the above data it is difficult to make a definiteassignment of the possible structure of the complexes i. e. the trans-(I) or thecis-(II)-square plan ar geometry. The relatively high intensity of the d-d bands(ef. the electronic spectral data) may be in favour of the cis-form as it hasa lower (local) symmetry than the tmns-form.Monodentate, mixed bidentate and monodentate, and mixed bidentate andbridging phosphanes are known in the literature for some nickel(II) phosphanecornplexes.PEXPERIMENTALAll chemicals were of analytical grade. The alkylxanthatonickel(II) precursorswere prepared folloving published procedures.š'? IR spectra were obtained usingpotassium bromide pellets with a Perkin Elmer 599B recorđing spectrophotometer.Electronic spectra were obtained with a Shimadzu UV-200S and matched 1.0 cmquartz cells. Conductance measurements were made on tresh solutions (10-3 M) in aLF Digi 550 conductance bridge. Proton nuclear magnetic resonance spectra wererecord ed on a Varian EM-390 NMR 90 MHz spectrometer. Tetramethylsilane (TMS)was employed as an external standard. Thermal gravimetric analysis was deter-mined with a 1090 Du pont thermal analyzer, with a furnace heating rate of 10=cper minute.Bis( alky lxanthato )bis(bisdiphen y l phosphino )ethanenicke l( II)To a 20 ml chloroform solution of bis(alkylxanthato)nickel(II) (3.3 mmole) a solu-tion of bis(diphenylphosphino)ethane (3.3 mm ole) in 20 ml chloroform was added atcontinuous stirrmg. The solution mixture turned red and after addition of diethyl-ether and cooling in ice bath microcrystalline red to orange precipitates wereobtained. The products were filtered, washed with acetone and dried over P,jOl0.IR-spectrum of e. g. Ni (Mexani-rdpei»: 1180, 1'." C-O-C, 1090, 1', C-O-C, 1020, 'vC=S, 740, 710, 700 cm" l' PPh2 + e CH2-.Bis( alkylxanthato )bis(bisdiphenylphosphino )bntanenickel( II)The complexes were prepared in the same way as mentioned above. Yellow topale brown precipitates were isolated, which were collected, washed with acetoneand dried over P4010. IR-spectrum of e. g. Ni (Etxanj-tdpbi«: 1189, 'V" C-O-C, 1095,1', C-OC, 1020, 'v C=S, 770, 740, 720, 710 cm-I, 'V PPhz + (} CHz-.AcknowLedgement. - The authors are thankful to dr. N. A f i f i, Physics De-partment, Faculty of Science, Assiut University, for the therrnal measurements.COMPLEXES OF Ni (II) ALKYLXANTHATES 161REFERENCE S1. G. J. M. Van der k e r k and H. L. K lo p P i n g, Red. Trav. Chim. Pays--Bas. 71 (1952) 1179; Nature (London) 176 (1955) 308.2. J. W. War k and A. B. Cox, Trans. Am. I.M.M.E. 134 (1946) 64.3. D. C o u c o u van i s, Prog. Inorg. Chem. 11 (1970) 233.4. R. E i s e n b e r g, Prog. Inorg. Chem. 12 (1970) 295.5. S. R. Rao, Xanthates and Related Compounds, Marcel Dekker, Inc., NewYork, (1971).6. D. Co uc o u vani s and J. P. F a c kl er, Inorg. Chem. 6 (1967) 2047.7. R. N. Mu r t s. R. N. Da s h, and D. V. Ram ana R a s, J. Indian Chem.Soc. LXI (1984) 943.8. J. Za gal and J. A. C o s t ama g n a, J. lnorg. Nuct, Chem. Lett. 13 (1977)411.9. C. A. To 1man, Chem. Rev. 77 (1977) 313.10. G. W. W a t t and B. J. Mc Cor m i c k, Spectrochim. Acta 21 (1965) 753.11. T. Web b, C. C h eng, E. He avi i n, and R. A. Li t tle, lnorg. Chim.Acta 49 (1981) 107.12. R. K. G u P t a, A. K. R a i, R. C. Me h r o t r a, and V. K. J a i n, Polyhe-dron 3 (1984) 721.13. A. A. M. Al y, A. A. Mo ham e d, M. A. M o u s a, and M. El - S h a-b a s y, Chem. Scripta 24 (1984) 196.14. A. B. P. Lever, lnorganic Electronic Spectroscopy, Elsevier, New York (1968).15. A. A. M. Al s, M. M. Ka m a 1, M. S. El - Mei i g s. and A. I. El - S aid,Z. Naturforsch. 39b (1984) 1676.16. A. A. M. Al y, M. M. K ama 1, M. S. El - Mei i g s. and A. I. El - S aid,Chem. Scripta 25 (1985) 249.17. M. Chikuma, A. Yokoyama, and H. Tanaka, J. lnorg. NucL Chem.36 (1974) 1243.18. K. K. C how and C. A. Mc A u 1i f f e, lnorg. Chim. Act. 16 (1974) 197.19. G. W. W a t t and B. J. Mc Cor m i ck, J. Inorq. NucL Chem. 27 (1965) 898.SAŽETAKNovi mješoviti kompleksi ditercijarnih fosfana s nikal(II)-alkilksantatimaAref A. M. Aly, Mostafa M. Kamal, Mahmouđ S. El-Meligy i Asma I. El-SaidPripravljani su mješoviti kompleksi nikla (II) s alkilksantatima i ditercijarnimfosfanima; opći im je sastav Ni(ROCSSl2(diphosl2 (R: Me, Et, Pr, Bu, cikloheksil;diphos: bis( difenilfosfino )etan, bis( difenilfosfino )butan).Na osnovi elementne analize, elektronskih, vibracijskih i NMR spektara, kao imjerenja vodljivosti i termičke analize, za te je komplekse predložena kvadratnaplanarna struktura.r

New Mixed Ligand Complexes of Ditertiary Phosphanes with Ni(II) Alkylxanthates

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